getDiffRanges: better fallback for absent patch

lib/analyze.js

@@ -243,6 +243,12 @@ async function getFileDiffsWithBasehead(baseRef, headLabel, logger) {
     }
 }
 function getDiffRanges(fileDiff, logger) {
+    // Diff-informed queries expect the file path to be absolute. CodeQL always
+    // uses forward slashes as the path separator, so on Windows we need to
+    // replace any backslashes with forward slashes.
+    const filename = path
+        .join(actionsUtil.getRequiredInput("checkout_path"), fileDiff.filename)
+        .replaceAll(path.sep, "/");
     if (fileDiff.patch === undefined) {
         if (fileDiff.changes === 0) {
             // There are situations where a changed file legitimately has no diff.
@@ -253,17 +259,16 @@ function getDiffRanges(fileDiff, logger) {
             return [];
         }
         // If a file is reported to have nonzero changes but no patch, that may be
-        // due to the file diff being too large. In this case, we should return
+        // due to the file diff being too large. In this case, we should fall back
-        // undefined to indicate that we cannot process the diff.
+        // to a special diff range that covers the entire file.
-        logger.warning(`No patch found for file ${fileDiff.filename} with ${fileDiff.changes} changes.`);
+        return [
-        return undefined;
+            {
+                path: filename,
+                startLine: 0,
+                endLine: 0,
+            },
+        ];
     }
-    // Diff-informed queries expect the file path to be absolute. CodeQL always
-    // uses forward slashes as the path separator, so on Windows we need to
-    // replace any backslashes with forward slashes.
-    const filename = path
-        .join(actionsUtil.getRequiredInput("checkout_path"), fileDiff.filename)
-        .replaceAll(path.sep, "/");
     // The 1-based file line number of the current line
     let currentLine = 0;
     // The 1-based file line number that starts the current range of added lines

lib/analyze.test.js

@@ -146,7 +146,13 @@ function runGetDiffRanges(changes, patch) {
 });
 (0, ava_1.default)("getDiffRanges: file diff too large", async (t) => {
     const diffRanges = runGetDiffRanges(1000000, undefined);
-    t.deepEqual(diffRanges, undefined);
+    t.deepEqual(diffRanges, [
+        {
+            path: "/checkout/path/test.txt",
+            startLine: 0,
+            endLine: 0,
+        },
+    ]);
 });
 (0, ava_1.default)("getDiffRanges: diff thunk with single addition range", async (t) => {
     const diffRanges = runGetDiffRanges(2, [
@@ -303,4 +309,8 @@ function runGetDiffRanges(changes, patch) {
         },
     ]);
 });
+(0, ava_1.default)("getDiffRanges: malformed thunk header", async (t) => {
+    const diffRanges = runGetDiffRanges(2, ["@@ 30 +50,2 @@", "+1", "+2"]);
+    t.deepEqual(diffRanges, undefined);
+});
 //# sourceMappingURL=analyze.test.js.map

src/analyze.test.ts

@@ -144,7 +144,13 @@ test("getDiffRanges: file unchanged", async (t) => {
 
 test("getDiffRanges: file diff too large", async (t) => {
   const diffRanges = runGetDiffRanges(1000000, undefined);
-  t.deepEqual(diffRanges, undefined);
+  t.deepEqual(diffRanges, [
+    {
+      path: "/checkout/path/test.txt",
+      startLine: 0,
+      endLine: 0,
+    },
+  ]);
 });
 
 test("getDiffRanges: diff thunk with single addition range", async (t) => {
@@ -308,3 +314,8 @@ test("getDiffRanges: no diff context lines", async (t) => {
     },
   ]);
 });
+
+test("getDiffRanges: malformed thunk header", async (t) => {
+  const diffRanges = runGetDiffRanges(2, ["@@ 30 +50,2 @@", "+1", "+2"]);
+  t.deepEqual(diffRanges, undefined);
+});

src/analyze.ts

@@ -387,6 +387,13 @@ function getDiffRanges(
   fileDiff: FileDiff,
   logger: Logger,
 ): DiffThunkRange[] | undefined {
+  // Diff-informed queries expect the file path to be absolute. CodeQL always
+  // uses forward slashes as the path separator, so on Windows we need to
+  // replace any backslashes with forward slashes.
+  const filename = path
+    .join(actionsUtil.getRequiredInput("checkout_path"), fileDiff.filename)
+    .replaceAll(path.sep, "/");
+
   if (fileDiff.patch === undefined) {
     if (fileDiff.changes === 0) {
       // There are situations where a changed file legitimately has no diff.
@@ -397,21 +404,17 @@ function getDiffRanges(
       return [];
     }
     // If a file is reported to have nonzero changes but no patch, that may be
-    // due to the file diff being too large. In this case, we should return
+    // due to the file diff being too large. In this case, we should fall back
-    // undefined to indicate that we cannot process the diff.
+    // to a special diff range that covers the entire file.
-    logger.warning(
+    return [
-      `No patch found for file ${fileDiff.filename} with ${fileDiff.changes} changes.`,
+      {
-    );
+        path: filename,
-    return undefined;
+        startLine: 0,
+        endLine: 0,
+      },
+    ];
   }
 
-  // Diff-informed queries expect the file path to be absolute. CodeQL always
-  // uses forward slashes as the path separator, so on Windows we need to
-  // replace any backslashes with forward slashes.
-  const filename = path
-    .join(actionsUtil.getRequiredInput("checkout_path"), fileDiff.filename)
-    .replaceAll(path.sep, "/");
-
   // The 1-based file line number of the current line
   let currentLine = 0;
   // The 1-based file line number that starts the current range of added lines